PROJECT SUMMARY Exposure to traffic related air pollution (TRAP) is known to trigger childhood asthma symptoms and likely contributes to the disparity in asthma prevalence and morbidity in urban communities. Regular physical activity can improve asthma symptoms. However, increased minute ventilation (ie respiratory rate x tidal volume) during activity may increase deposition of pollutant particles into the airways. Thus, pollution may offset the respiratory benefits of physical activity. One of the challenges of accurately assessing the combined effects of pollution and activity on the airways is that inhaled dose of pollutants could vary by proximity to exposure source and by individual differences in minute ventilation. Therefore, our objective is take an individualized approach to assess change in minute ventilation during childhood activities while also considering variability in home and school exposure to TRAP. We hypothesize that the positive association between exposure to TRAP and asthma symptoms will be most significant among children that are 1) highly physically active and 2) have larger increases in minute ventilation in response to physical activity. In order to address this hypothesis we will take advantage of 2 existing cohorts of children with differing severity of asthma that are enrolled in the Inner City Asthma Consortium (ICAC) studies. For our first aim we will examine the interaction between exposure to TRAP (assessed at home and school using geographic information systems (GIS) technology) and physical activity (assessed by validated questionnaire) on asthma symptoms. We will evaluate these associations in: 1) a cross-sectional cohort of 320 moderate-severe asthmatics, ages 6-17 that live in 10 urban US cities and 2) a 3 year longitudinal cohort of 150 mild-moderate asthmatics, ages 12-16 that live in 4 urban US cities. For our second aim we will recruit a sub-sample of 40 children with mild- moderate asthma that live in New York City. We will combine individual cardiopulmonary exercise testing (CPET) with 72-hour accelerometry measurements to determine the magnitude of increase in minute ventilation in response to usual childhood activities. Then we will use these values to determine if larger individual increases in minute ventilation influence the relationship between exposure to TRAP and asthma symptoms. With an enhanced understanding of individual susceptibility to environmentally triggered asthma, we will be better equipped to address and remediate the disproportionate risk of asthma morbidity among urban children.